1. Field of the Invention
The present invention relates to a laser induced thermal imaging apparatus including a stage grounded by a grounding means to control static electricity, and a method of fabricating an organic light emitting display (OLED) using the same.
2. Description of the Related Art
Recently, an OLED is attracting attention as a next generation display, since the OLED has low voltage driving, high luminous efficiency, wide viewing angle and rapid response speed characteristics to display high resolution motion pictures.
In addition, the OLED is a self-emissive display which is formed of an organic layer including an organic emission layer between an anode electrode and a cathode electrode, and emits light by recombination of holes and electrons in the organic emission layer when a voltage is applied between the two electrodes so that the OLED does not need a separate backlight used in an LCD, thereby manufacturing light-weight and slim-sized OLED and simplifying the process.
In this process, the OLED may be classified into a small molecule OLED and a polymer OLED according to materials of the organic layer, particularly, the organic emission layer.
The small molecule OLED is formed of a plurality of organic layers having different functions between an anode electrode and a cathode electrode, including a hole injection layer, a hole transport layer, an emission layer, a hole blocking layer, an electron injection layer and so on, thereby enabling adjustment by doping impurities into the organic layers to prevent accumulation of charges or replacing the organic layers with a material having an appropriate energy level. In this process, since the organic layers are generally formed by a vacuum deposition method, it is difficult to realize a large-sized display.
On the other hand, the polymer OLED may be formed in a single layer structure including an organic emission layer between an anode electrode and a cathode electrode, or a dual-layer structure further including a hole transport layer, thereby manufacturing an OLED with thin layers. In addition, the organic layer can be manufactured under a normal pressure since it is formed by a wet coating method, thereby reducing the manufacturing cost and easily fabricating a large-sized display.
In case of manufacturing a monochrome device, the polymer OLED can be readily manufactured using a spin coating process, but has lower efficiency and life span characteristics compared to the small molecule OLED. In addition, in case of a full color device, an emission layer representing primary colors of red (R), green (G) and blue (B) can be patterned on the OLED to realize a full color device. In this process, the organic layer of the small molecule OLED can be patterned by a deposition method using a shadow mask, and the organic layer of the polymer OLED can be patterned by an inkjet printing method or a laser induced thermal imaging (LITI) method. Among them, the LITI method can make the OLED have excellent intra-pixel uniformity when the large-sized display is performed, since the LITI method can use the characteristics of the spin coating method. In addition, since the LITI method is a dry process rather than a wet process, it is possible to solve a reduction of life span due to a solvent, and finely pattern the organic layer.
In order to employ the LITI method, basically, a light source, OLED substrates, i.e., a substrate and a donor substrate are required, and the donor substrate is formed of a base layer, a light-to-heat conversion layer, an intermediate layer, and an organic layer.
The LITI method includes absorbing light emitted from the light source into the light-to-heat conversion layer to convert the light to heat energy, and transferring an organic material formed on a transfer layer to the substrate using the converted heat energy.
A method of forming a pattern of an OLED using the LITI method is disclosed in Korean Patent Registration No. 10-342653, and U.S. Pat. Nos. 5,998,085, 6,214,520 and 6,114,085.
FIGS. 1A to 1C are cross-sectional views illustrating an organic layer patterning process using an LITI method.
Referring to FIG. 1A, a substrate 10 is provided, and a donor substrate 20 including a base layer 21, a light-to-heat conversion layer 22 and an organic layer 23 is laminated on the substrate 10.
Then, as shown in FIG. 1B, light by a laser X is irradiated on a first region (a) of the base layer 21 of the donor substrate 20. The light passed through the base layer 21 is converted to heat in the light-to-heat conversion layer 22, and the adhesion between the organic layer 23 and the light-to-heat conversion layer 22 in the first region (a) is degraded due to the heat.
Then, as shown in FIG. 1C, after the organic layer 23, which has the degraded adhesion, i.e., in the first region (a) is transferred onto the substrate 10, when the donor substrate 20 is detached from the substrate 10, the transferred organic layer 23a is attached on the substrate 10, and the organic layer 23b in the second region (b), at which the light is not irradiated, is detached from the substrate 10 together with the donor substrate 20, thereby forming a patterned organic layer 23a. 
However, in forming the patterned organic layer using the LITI method, static electricity may be generated due to friction and the other environmental factors, during the lamination and delamination processes of the donor substrate 20 and the substrate 10. Since such a static electricity has a discharge voltage of several thousand to several tens of thousand volts, it is likely to generate failures of the device such as a short-circuit ofjointed parts due to the static electricity, melting of a metal due to a temperature increase in the device, separation of an interconnection, and so on. Moreover, the static electricity may affect an inner circuit of the device to thereby degrade the device characteristics.